1. Field of the Invention
This invention relates to a reclosable package and to a method for producing the same. More specifically this invention relates to a reclosable package for food products where the package is evacuated and hermetically sealed within an interlocking strip.
2. Description of the Prior Art
A substantial volume of cheese, bacon frankfurters, sliced luncheon meat and other processed meats are sold in packages which are formed from flexible thermoplastic materials. The freshness of the product within the package is to a large measure dependent upon the fact that the thermoplastic package is hermetically sealed and has been evacuated and, in some instances, gas flushed. However, in many instances, when an evacuated package of this type is purchased not all of its contents are used at once by the consumer. When the initial seal has been broken and part of the package removed it is difficult to reclose the package for satisfactory storage in a refrigerator; and, in order to preserve the contents in a fresh state without loss of flavor and texture, it is often necessary to completely repackage the product. To overcome this problem, there are many prior art package designs which offer means of opening and resealing but many of these have the disadvantage that wordy printed directions are needed and many times the thermoplastic packaging material is so stiff and so strong that even a carefully designed reclosure device can be destroyed.
Another problem which is encountered with prior art reclosable packages is the problem of manufacturing them at a commercially acceptable rate. Placing tear tabs, tear strips, or the like in combination with resealing means such as pressure sensitive adhesive strips calls for extreme care in registration and alignment of each of the packaging components and rather precise sealing must take place in order to achieve a satisfactory product. Accordingly, some manufacturers and methods for producing a reclosable package use what is commonly referred to as closure strips on each of the two inner surfaces of the packaging material. These closure strips consist of thermoplastic beads either extruded or attached to the packaging materials. These beads have an interlocking profile. Several patents in this area have been issued. However, the closure strip is always found within the confines of the hermetic seal of the package. Such a process means that the closure strip must be indented from the edge of the packaging material and after sealing the closure strip forms voids and pockets within the package and product cavity itself.
U.S. Pat. No. 4,246,288 and U.S. Pat. No. 4,437,293 describe a reclosable package and a method and apparatus for making such a reclosable package.
U.S. Pat. No. 3,647,485 describes a package and a method for making the same which has an improved hermetic breakaway or peelable seal formed between an ethylene-polar monomer polymer film or coating and a thermoplastic film.
U.S. Pat. No. 3,740,237 describes a continuous method of enclosing the product between a pair of films so as to provide a package having a product enclosing portion and a peripheral flange. The pair of films are joined to form a hermetic dual seal by applying a continuous strip of peelable bond adhesive through a portion of the film destined to become a peripheral flange and extending partially into that portion of the film destined to become the product enclosing portion and providing the remainder of the peripheral flange with means for permanently bonding the pair of films.
U.S. Pat. No. 4,273,815 describes an improved laminated film having at least one lamina of polyvinylidene chloride film adhered to at least one lamina of chlorinated polyethylene, and the method of forming this improved lamina, and to packages produced therewith. Polyvinylidene chloride films, commonly known as Saran, are used extensively in the packaging of food products and the like which are susceptible to deterioration by oxygen and other gases. This film is adequately flexible and effectively impermeable to air and oxygen. In addition, polyvinylidene chloride films exhibit unique properties in a so-called "supercooled" or amorphous condition during which these films can be readily formed around a product to be packaged without incurring undesirable folds, pleats or the like.